Women [29] with premature labor were randomly assigned to a ritodrine (N = 14) or placebo (N = 15) drug group. The 2 groups were of similar age, parity, weight, gestational age and cervical change at the onset of treatment. They were treated sequentially with i.v., i.m. and oral drugs and monitored carefully during therapy. There was a significant increase in both the maternal and fetal heart rates during ritodrine treatment, and also a significant decrease in maternal blood pressure. Ritodrine-treated women often complained of palpitations. There was no significant difference in the extension of pregnancy, birth weight or infant survival for the ritodrine group. Although the 1 min Apgar scores in the ritodrine group were higher, the 5 min scores were similar in both groups.